The present invention relates generally to the field of electronics, and more particularly, to field emitters used in M-type microwave devices.
Well known are microwave devices such as that disclosed in Russian Patent N 2007777, which have field emission cathodes having interfaces for the purpose of preventing of thermal diffusion of corrosively active materials. These interfaces are shaped as discs made of thicker material which are placed on both sides of field emitter operating film made of foil of 0.5 to 5 xcexc thick. One of the drawbacks of Russian Patent ""777 is a limitation of the thickness of the foil used as the field emitter. It is just impossible to assemble such emitter at a definite thickness of the foil. Besides, non-uniform thermal contact between the operating film and protective discs along the circumference does not allow heat to be effectively carried off from the field emitter during its operation. This may lead to damage of the field emitter because of overheating and melting.
Also known are other types of microwave devices such as that disclosed in Russian Patent N 1780444 where a two-layer structure, consisting of the field emitter operating film applied on the foil substrate, is used as a field emitter. The basic drawback of Russian Patent ""444 is that one side of the operating film is not protected from mechanical and diffusion processes effecting the film both during assembly and operation of device. This reduces its mechanical strength and reliability as well as lifetime of the whole field emitter.
It is, therefore, an object of the present invention to provide a field emitter having lower built-in mechanical stress than prior art field emitters.
The present invention relates to electronics and particularly to field emitters used in M-type microwave devices. The design of a multi-layer field emitter is proposed which has at least one operating film and supporting films, providing mechanical strength and preventing penetration of corrosion materials into the operating film at high operating temperatures. The supporting films could be produced from the same material or material with linear expansion coefficients equal or close to that of the operating film material. Built-in mechanical stress can cause not only deformation but also a break of the film during its exploitation in a wide range of temperatures. In the inventive structure the thermal stresses in the operating film during an emission from its surface are lower due to good thermal contact with supporting films.
General advantages of the field emitter of the present invention compared to the prior art is that the present invention is mechanically stronger and more reliable which makes the cathode assembly easier. The present invention has a minimum of mechanical tensions which provides safe operation in a wide temperature range. The present invention provides operation at the contact with corrosively active materials under high temperature.
The operating film of the field emitter of the present invention could be as thin as a few angstroms which provides using this design in a variety of devices. At the same time, supporting films have a direct contact with the operating film which allows carrying off heat effectively from the emitter during its operation.
Production of the described field emitters is based on well developed technological processes used in mass production of thin film circuits and allows to make on their base inexpensive mono- and multi-emitter systems.
These and other objects of the present invention are achieved by a method of manufacturing a field emitter for a magnetron including depositing three layers of film on a substrate, placing at least one protective mask on an uppermost layer of three layers, etching the three layers not protected by the at least one protective mask, exposing horizontal and vertical portions of the first and third layers of the remaining three layers, and removing the protective mask and the substrate leaving at least one field emitter.
The foregoing objects of the present invention are achieved by a method of manufacturing a field emitter for a magnetron including depositing three layers of film on a substrate, placing at least one protective mask on an uppermost layer of the three layers, etching the three layers not protected by the at least one protective mask, depositing an additional film layer, partially etching the first of the three layers of film, removing the layers of film and photoresist above the partially etched layer, depositing a layer of film on the remaining partially etched layer and the additional layer, removing the partially etched layer and the layer of film above the partially etched layer, sputtering additional areas corresponding in shape to the remaining etched layer, and building up an additional layer depositing an additional layer on the sputtered areas.
Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive.